The invention relates to a process and a device for cooling hot rolled metal plates and strips, especially such of aluminium or an aluminium alloy in which a hot rolled strip is cut to plates or strips after it emerges from a rolling mill.
As it leaves a hot-rolling mill, a hot-rolled strip is normally at a temperature of approximately 300.degree. to 500.degree. C. In order to manufacture plates out of this, the hot-rolled strip is cut immediately after it leaves the hot-rolling mill. As there is no suitable seal-proof material for suction pads that can be employed at temperatures above 300.degree. C., the hot plates have to be removed from the hot line by means of grappling tools which enable the plates to be stacked. This handling of the plates is labour intensive and undesirable marks from the grappling tools may remain on the surface of the plates. Rapid cooling of the plates could in principle be achieved by means of the rolling emulsion during a series of roll-passes without any reduction in thickness. The large differences in temperature this would produce in the hot-rolled strip would, however, lead to unacceptable deviations in flatness of the plates.
If a hot-rolled strip is to be rolled further, it is often also advantageous to cool the strip as it is introduced into the tandem mill of a finishing line or in a reversing stand. It is, however, important that no deviations in flatness are produced as a result of this form of cooling.
Known from the European patent EP-A-343 103 is a process for cooling extruded sections and rolled strip, by means of which water mist is created for cooling purposes. Because of the small amount of heat transfer, however, this process is not suitable for rapid in-line cooling of hot rolled plate thicker than about 5 mm. This previously known method of cooling with spray nozzles is described in EP-A-0 429 394 for cooling cast metal strands.
Described in EP-A-0587 607 is an in-line method for cooling sections emerging from an extrusion press, whereby the spray nozzles described in EP-A-0343 103 are employed, built in as modules.
In view of the above, the object of the present invention is to provide a process and a device of the kind described at the start, by means of which plates and strips can be cooled in a controlled manner and as fast as possible to a temperature of about 250.degree. C. at maximum, without deviations in flatness occurring in the plates.